It depends what you want your class to do. Take a look at the Hierarchy Chart | Microsoft Docs[^] and see if there is an existing control that you can derive from (even if it is CWnd), since the base class will provide lots of functionality.
Because all MFC controls are CWnd based you should use that as base class too. Then add the painting (OnPaint, OnEraseBackground), register the window class and add control specific message handlers as necessary.
I'm new to MFC and after passing several hours trying to solve a problem (that might seem simple to most of you), I decided to post my question here in order to get your help and hints.
I'm developing an MFC (C++) application using Visual Studio 2017. The application contains a main CDialog to communicate with a 2D Laser sensor using TCP/IP and to plot the points detected by the sensor on screen in real time (this is done on an IDC_PICTURE element with OnPaint() as the following:
// I create the pDC, memDC and the compatible device/bitmap
CDC* pDC = m_Picture.GetDC(); // m_picture is a member CStatic element in the main CDialog class
bmp.CreateCompatibleBitmap(pDC, PicW, PicH); // PicW, PicH are the width and height of the associated CRect member object in the class // After that, I get the points to plot in order to write them to my memDC//then, I copy the memDC to the device and delete the memDC, release the pDC
pDC->StretchBlt(0, 0, PicW, PicH, &memDC, 0, 0, PicW, PicH, SRCCOPY);
This previously mentioned code is working very well without problems with the main dialog.
Long story short, my problem is the following:
On that same dialog, I created a button that opens a secondary modeless dialog that contains another IDC_PICTURE element. The main goal of the secondary dialog is to plot a delayed version (t-n) of the points seen by the Laser sensor. My main problem is that I am not being able to show anything on the secondary IDC_PICTURE. Is it wrong to do the same thing applied on the main dialog (on another IDC_PICTURE, with anothe pDC and memDC)?
The secondary dialog is defined in a separate class of which I have created an instance in the (first) main CDialog class.
I have been looking everywhere on solutions that could look similar to my problem, but I haven't found anything. What exactly am I missing?
PS. sorry if my problem description isn't clear enough. My code is getting too big to be copied/pasted.. I'd be very happy if you have any hints / questions that might make me find the solution..
I guess that you trigger it in the main dialog when new data has been received from the sensor. You have to do it similar for the second modeless dialog (e.g. by triggering a repaint after new data has been passed).
I actually don't know what this message is or how to handle it.
Then you are definitely going to have problems, especially if you are trying to paint the controls at other times. If you do not understand how Window painting works in Windows then you will continue to have problems. I suggest you look for some tutorials on how it is done.
I was looking to intercept a Rich Edit controls keystrokes, seems I have call CRicheditctrl::SetEventmask with ENM_KEYEVENTS> this lead me to a article about notification When a Rich Edit is resized
The Author Thales P. Carvalho has the notification method OnRequestResize in the parent window. I cannt seem to find this method in either Cdialog or CWnd maybe he was referring to OnNotify ?
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"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer
at best, i would think the behavior is undefined. the function is going to try to find a parameter, somewhere. maybe it pulls some random garbage off the stack where it expects a parameter to be, or maybe your compiler puts variables into certain registers (and so the function will just grab random garbage out of a register).
You shoud correct your caller.h to have the correct prototype for A(). Then #include caller.h in both where you define A() and where you invoke it.
This "works", due to C calling conventions, where the caller is responsible for pushing and popping arguments off the stack. In your case the caller doesn't push anything on the stack. When A() executes it will use whatever values are on the stack as its parameters, which in this case could be any value at all.
Further to this, in C the declaration void f(); does not declare a function with no parameters, but declares a function with an unknown number of parameters. If you know that a function takes no arguments, you should prototype it as void f(void);. Otherwise, the compiler will happily let you do the following:
Using gcc I can compile the above with -Wall -Wextra, and get no warnings. If I add -Wstrict-prototypes, I do get the warning "function declaration isn’t a prototype [-Wstrict-prototypes]. If you're using MS-VSC, there's probably a similar warning flag that you can use.
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